Hair consists of many long, parallel chains of amino acids. These chains, or polymers, of amino acids are bound to each other via 1) hydrogen bonding, 2) salt bridges between acid and base groups, and 3) disulfide bonds.
At alkaline pH, the disulfide bonds in hair can be broken (Dombrink et al., Chem Matters, 1983, page 8). For example, lye-based relaxers contain hydroxide ions, which can attack disulfide linkages. Cleavage of disulfide bonds by the lye-based relaxer achieves straightening of the hair by changing the relative positions of polypeptide chains. Rinsing the hair and/or applying a neutralizing formulation complete the straightening process.
While lye and other alkali-based relaxers are highly effective at relaxing and straightening hair, they can result in reduction of hair strength and potential loss of hair through breakage. Lye and alkali-based relaxers are not used to perm hair.
Traditional perms use thiol or sulfur-containing reducing agents followed by a second oxidizing step, typically using hydrogen peroxide, to set the hair. These thiol or sulfur-containing reducing agents are foul smelling and, if not properly rinsed between the steps, can damage and/or brake hair.
Thus, there is a need for hair curling formulations and treatments, which provide improved conditioning benefit for hair when the hair is curled. There is a need to provide long lasting moisturized feel, smooth feel, and manageability control to curled hair.
There is also a need for hair curling formulations and treatments that afford the ability to tune or select the level of curl imparted to hair.
There is a further need for hair curling formulations and treatments that can be applied to the hair as a single formulation.
Additionally, there is a need for hair curling formulations without a foul-smelling thiol or sulfur-containing agent, or related odors therefrom.
Therefore, it is an object of this invention to provide improved curling formulations and curling methods for repairing and/or strengthening curled hair.
It also is an object of this invention to provide curling formulations and methods that can be used to tune or select the level of curl imparted to hair.
It is a further object of this invention to provide hair curling formulations and treatments that can be applied to the hair as a single formulation, as well as formulations without a foul-smelling thiol or sulfur-based odor.